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Abstract:

A method of operating an exhaust gas heat recovery (EGHR) system in a
vehicle including an engine, a transmission, and an EGHR heat exchanger
is provided. The method includes monitoring an engine water temperature
and may include monitoring a transmission oil temperature and an ambient
air temperature. The method includes comparing the monitored engine water
temperature to one or more calibrated engine temperatures. Based upon the
monitored temperatures and comparison to the calibrated temperatures, the
method controls a two-way valve. The two-way valve is configured to be
set to one of an engine position and a transmission position. The engine
position allows heat-exchange communication between the EGHR heat
exchanger and the engine, and the transmission position allows
heat-exchange communication between the EGHR heat exchanger, the
transmission, and the engine.

Claims:

1. A method of operating an exhaust gas heat recovery (EGHR) system in a
vehicle including an engine, a transmission, and an EGHR heat exchanger,
the method comprising: controlling a two-way valve, wherein the two-way
valve is configured to be set to one of an engine position and a
transmission position, wherein the engine position allows heat-exchange
communication between the EGHR heat exchanger and the engine and the
transmission position allows heat-exchange communication between the EGHR
heat exchanger, the transmission, and the engine; monitoring an engine
water temperature; comparing the monitored engine water temperature to a
calibrated first engine temperature; and if the monitored engine water
temperature is below the calibrated first engine temperature, setting the
two-way valve to the engine position.

2. The method of claim 1, further comprising: monitoring a transmission
oil temperature; comparing the monitored transmission oil temperature to
a calibrated first transmission temperature; and if the monitored
transmission oil temperature is below the calibrated first transmission
temperature and the monitored engine water temperature is below the
calibrated first engine temperature, setting the two-way valve to the
transmission position.

3. The method of claim 2, further comprising: monitoring an ambient air
temperature; comparing the monitored ambient air temperature to a
calibrated hot ambient temperature; if the monitored ambient air
temperature is greater than the calibrated hot ambient temperature,
comparing the monitored engine water temperature to a calibrated extreme
engine temperature; and if the monitored engine water temperature is less
than the calibrated extreme engine temperature, setting the two-way valve
to the engine position.

4. The method of claim 3, wherein the vehicle further includes a
transmission radiator, and further comprising: if the monitored engine
water temperature is greater than the calibrated extreme engine
temperature, comparing the monitored transmission oil temperature to a
calibrated extreme transmission temperature; and if the monitored
transmission oil temperature is below the calibrated extreme transmission
temperature, setting the two-way valve to the transmission position, such
that the transmission radiator is in heat-exchange communication with the
engine.

5. The method of claim 4, further comprising: if the monitored engine
water temperature is greater than the calibrated extreme engine
temperature and the monitored transmission oil temperature is greater
than the calibrated extreme transmission temperature, setting the two-way
valve to the engine position, such that the transmission radiator is not
in heat-exchange communication with the engine.

6. The method of claim 5, further comprising: comparing the monitored
ambient air temperature to one of a calibrated cold ambient temperature,
a calibrated mild ambient temperature, and the calibrated hot ambient
temperature; if the monitored ambient air temperature is below the
calibrated cold ambient temperature, comparing the monitored engine water
temperature to a calibrated second engine temperature, wherein the
calibrated second engine temperature is greater than the calibrated first
engine temperature; and if the monitored engine water temperature is
below the calibrated second engine temperature, setting the two-way valve
to the engine position.

7. The method of claim 6, further comprising: monitoring for an auto-stop
mode, wherein the auto-stop mode occurs when the engine is not producing
positive torque; if the engine is in the auto-stop mode and if the
monitored ambient air temperature is below the calibrated cold ambient
temperature, comparing the monitored transmission oil temperature to a
calibrated second transmission temperature, wherein the calibrated second
transmission temperature is less than the calibrated first transmission
temperature; and if the monitored transmission oil temperature is below
the calibrated second transmission temperature, setting the two-way valve
to the transmission position.

10. A method of operating an exhaust gas heat recovery (EGHR) system in a
vehicle including an engine, a transmission, a transmission radiator, and
an EGHR heat exchanger, the method comprising: controlling a two-way
valve, wherein the two-way valve is configured to be set to one of an
engine position and a transmission position, wherein the engine position
allows heat-exchange communication between the EGHR heat exchanger and
the engine and the transmission position allows heat-exchange
communication between the EGHR heat exchanger, the transmission, and the
engine; monitoring an engine water temperature; monitoring a transmission
oil temperature; monitoring an ambient air temperature; and comparing the
monitored ambient air temperature to a calibrated hot ambient
temperature, and: if the monitored ambient air temperature is greater
than the calibrated hot ambient temperature, comparing the monitored
engine water temperature to a calibrated extreme engine temperature, if
the monitored engine water temperature is less than the calibrated
extreme engine temperature, setting the two-way valve to the engine
position, if the monitored engine water temperature is greater than the
calibrated extreme engine temperature, comparing the monitored
transmission oil temperature to a calibrated extreme transmission
temperature, and if the monitored transmission oil temperature is below
the calibrated extreme transmission temperature, setting the two-way
valve to the transmission position, such that the transmission radiator
is in heat-exchange communication with the engine.

11. The method of claim 10, further comprising: if the monitored engine
water temperature is greater than the calibrated extreme engine
temperature and the monitored transmission oil temperature is greater
than the calibrated extreme transmission temperature, setting the two-way
valve to the engine position, such that the transmission radiator is not
in heat-exchange communication with the engine.

12. The method of claim 11, further comprising: comparing the monitored
ambient air temperature to one of a calibrated cold ambient temperature,
a calibrated mild ambient temperature, and the calibrated hot ambient
temperature; if the monitored ambient air temperature is below the
calibrated cold ambient temperature, comparing the monitored engine water
temperature to a calibrated second engine temperature, wherein the
calibrated second engine temperature is greater than the calibrated first
engine temperature; and if the monitored engine water temperature is
below the calibrated second engine temperature, setting the two-way valve
to the engine position.

13. The method of claim 12, further comprising: monitoring for an
auto-stop mode, wherein the auto-stop mode occurs when the engine is not
producing positive torque; if the engine is in the auto-stop mode and if
the monitored ambient air temperature is below the calibrated cold
ambient temperature, comparing the monitored transmission oil temperature
to a calibrated second transmission temperature, wherein the calibrated
second transmission temperature is less than the calibrated first
transmission temperature; and if the monitored transmission oil
temperature is below the calibrated second transmission temperature,
setting the two-way valve to the transmission position.

Description:

TECHNICAL FIELD

[0002] This disclosure relates to control of exhaust gas heat reclaim,
recovery, or recirculation systems for vehicles.

BACKGROUND

[0003] Internal combustion engines produce energy by combustion of a fuel
with an (usually) air in a combustion chamber. The combustion process in
internal combustion engines produces power to move the vehicle, usually
converting the linear motion within the combustion chamber to rotation,
but also produces heat.

[0004] The combustion products--uncombusted fuel, unused oxygen, and
byproducts, in the form of (often) hot exhaust gases--are expelled
through an exhaust system taking the combustion products away from the
engine. Exhaust gas heat recovery is designed to remove heat from the
exhaust gas of engines and transfer it elsewhere, such as to a water
circuit. The interior of the car may be warmed using exhaust heat, or
thermoelectric devices may produce electricity from the exhaust heat.

SUMMARY

[0005] A method of operating an exhaust gas heat recovery (EGHR) system in
a vehicle including an engine, a transmission, and an EGHR heat exchanger
is provided. The method includes monitoring an engine water temperature
and may include monitoring a transmission oil temperature and an ambient
air temperature. The method includes comparing the monitored engine water
temperature to one or more calibrated engine temperatures. Based upon the
monitored temperatures and comparison to the calibrated temperatures, the
method controls a two-way valve.

[0006] The two-way valve is configured to be set to one of an engine
position and a transmission position. The engine position allows
heat-exchange communication between the EGHR heat exchanger and the
engine, and the transmission position allows heat-exchange communication
between the EGHR heat exchanger, the transmission, and the engine.

[0007] The method may include comparing the monitored engine water
temperature to a calibrated first engine temperature, and if the
monitored engine water temperature is below the calibrated first engine
temperature, setting the two-way valve to the engine position. The method
may further include comparing the monitored transmission oil temperature
to a calibrated first transmission temperature, and if the monitored
transmission oil temperature is below the calibrated first transmission
temperature and the monitored engine water temperature is below the
calibrated first engine temperature, setting the two-way valve to the
transmission position.

[0008] The above features and advantages, and other features and
advantages, of the present invention are readily apparent from the
following detailed description of some of the best modes and other
embodiments for carrying out the invention, as defined in the appended
claims, when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic diagram of an exemplary hybrid vehicle
powertrain having an exhaust gas heat recovery (EGHR) system in
communication with an engine and a transmission;

[0010] FIG. 2 is a schematic flow chart diagram of an algorithm or method
for controlling an EGHR system, such as that shown in FIG. 1;

[0011] FIG. 3 is a schematic flow chart of a subroutine of the method
shown in FIG. 2, showing portions of the method for mild ambient
temperatures;

[0012] FIG. 4 is a schematic flow chart of another subroutine of the
method shown in FIG. 2, showing portions of the method for cold ambient
temperatures; and

[0013] FIG. 5 is a schematic flow chart of another subroutine of the
method shown in FIG. 2, showing portions of the method for extreme or hot
ambient temperatures.

DETAILED DESCRIPTION

[0014] Referring to the drawings, wherein like reference numbers
correspond to like or similar components whenever possible throughout the
several figures, there is shown in FIG. 1 a schematic diagram of an
exhaust gas heat recovery (EGHR) system, referred to generally as EGHR
system 10. The EGHR system 10 is in selective fluid flow and
heat-exchange communication with an internal combustion engine 12 and a
transmission 14 of a vehicle (not shown).

[0015] The engine 12 is drivingly connected to the transmission 14, which
may be a hybrid transmission having one or more electric machines (not
shown). Alternatively, the vehicle may include one or more electric
machines acting directly on the engine output or the transmission input.
The engine 12 releases exhaust gas through an exhaust pipe or exhaust
system 16, which includes an EGHR heat exchanger 18, as explained herein.

[0016] While the present invention is described in detail with respect to
automotive applications, those skilled in the art will recognize the
broader applicability of the invention. Those having ordinary skill in
the art will recognize that terms such as "above," "below," "upward,"
"downward," et cetera, are used descriptively of the figures, and do not
represent limitations on the scope of the invention, as defined by the
appended claims.

[0017] FIG. 1 shows a highly-schematic control architecture or control
system 20 for the EGHR system 10. The control system 20 may include one
or more components (not separately shown) with a storage medium and a
suitable amount of programmable memory, which are capable of storing and
executing one or more algorithms or methods to effect control of the EGHR
system 10. Each component of the control system 20 may include
distributed controller architecture, such as a microprocessor-based
electronic control unit (ECU). Additional modules or processors may be
present within the control system 20.

[0018] An engine water circuit 22 moves coolant or water from the engine
12 through, eventually, the EGHR heat exchanger 18. The engine water
circuit 22 is supplied with pressurized coolant by a primary pump (not
separately shown) incorporated with the engine 12. The primary pump may
be a mechanical pump driven by rotation of the engine 12. Depending upon
the operating conditions of the EGHR system 10, the coolant in the engine
water circuit 22 may be heated by the exhaust gases from the engine 12. A
transmission water circuit 24 is selectively connected to the engine
water circuit 22 by a two-way valve 26, which allows heat-flow or
heat-exchange communication between the transmission water circuit 24 and
the engine water circuit 22.

[0019] The two-way valve 26 is configured to be selectively controlled or
set to one of an engine position and a transmission position. The engine
position of the two-way valve 26 allows heat-exchange communication
between the EGHR heat exchanger 18 and the engine 12. The transmission
position allows heat-exchange communication between the EGHR heat
exchanger 18 and both the transmission 14 and the engine 12. When the
two-way valve 26 is in the transmission position, the transmission water
circuit 24 is supplied with coolant or water from the engine water
circuit 22 by the primary pump, if the primary pump is operating. A
transmission oil circuit 28 circulates lubricating and cooling oil from
the transmission 14. The two-way valve 26 may be electrically operated,
fluid operated (such as by a pilot valve), or operated in any suitable
manner to move between the engine position and the transmission position.

[0020] The exact boundaries and paths of the engine water circuit 22 and
the transmission water circuit 24 may vary slightly. The engine water
circuit 22 provides communication between the engine 12 and the EGHR heat
exchanger 18. The transmission water circuit 24 provides communication
between the engine water circuit 22 and the transmission oil circuit 28.
The two-way valve 26 has three ports: a first port or inlet port brings
water or coolant in from the heater core 30 or directly from the coolant
outlet of the engine 12; a second port links the inlet flow to the engine
water circuit 22 such that only the engine water circuit 22 has flow; and
a third port links the inlet flow to the transmission water circuit 24.

[0021] In addition to the EGHR heat exchanger 18, the EGHR system 10
includes other heat exchangers or radiators. A heater core 30 allows heat
to be transferred from the coolant or water leaving the engine 12 to the
cabin (passenger compartment) of the vehicle. An engine radiator 32 is a
water-to-air heat exchanger configured to selectively dissipate heat from
the engine 12 to ambient air flowing through the engine radiator 32. A
thermostat (not shown) may be used to control flow of coolant from the
engine 12 through the engine radiator 32. A transmission radiator 34 is
an oil-to-air heat exchanger configured to selectively dissipate heat
from the transmission oil circuit 28 of the transmission 14 to ambient
air flowing through the transmission radiator 34.

[0022] While the engine radiator 32 and the transmission radiator 34 are
shown schematically side-by-side, in many applications of the EGHR system
10, the engine radiator 32 and transmission radiator 34 would be placed
one in front of the other at an area of high airflow into the underhood
area of the vehicle. However, the engine radiator 32 and the transmission
radiator 34 may be located elsewhere in the vehicle. As used herein, heat
exchanger may refer to myriad different devices for exchanging heat
energy between two mediums or two systems.

[0023] The actual direction of flow of heat energy between any sides of a
heat exchanger is controlled by temperature difference across the
specific heat exchanger. For example, if the engine 12 were very cold and
the thermostat allowed circulation through the engine radiator 32 on a
very hot day, the engine radiator 32 would warm the coolant until it
reached (approximately) the ambient temperature and would then cool the
engine coolant when the coolant temperature exceeded the ambient
temperature.

[0024] A central heat exchanger 36 is an oil-to-water heat exchanger which
allows heat-exchange communication between the transmission oil circuit
28 of the transmission 14 and the transmission water circuit 24. The
central heat exchanger 36 allows heat to be transferred from the
transmission water circuit 24 to the transmission oil circuit 28 in order
to warm the transmission 14 and reduce slip loss. Furthermore, as
discussed herein, the central heat exchanger 36 also allows the
transmission 14 and transmission radiator 34 to dissipate excess heat
from the engine 12 during hot or extreme conditions.

[0025] An auxiliary pump 38 is disposed within the engine water circuit
22. The auxiliary pump 38 may be used to add pressure and increase flow
through the engine water circuit 22 and, selectively, the transmission
water circuit 24 when the need arises. Furthermore, when the engine 12 is
turned off or un-fueled by the hybrid vehicle controls (not shown
separately) the auxiliary pump 38 may be used as the main pressure source
for the engine water circuit 22 and the transmission water circuit 24.
Therefore, the auxiliary pump 38 may be used to supplement the primary
pump incorporated into the engine 12, may be used as the only pump when
the engine 12 and the primary pump are not operating, or may be used as
the sole pump for the engine water circuit 22 and the transmission water
circuit 24.

[0026] An EGHR bypass valve 42 controls flow of exhaust gases through the
EGHR heat exchanger 18. The EGHR bypass valve 42 is shown in its
non-bypass position, which allows flow of exhaust gases through the EGHR
heat exchanger 18 and allows heat-exchange communication between the
exhaust gases and the engine water circuit 22. When the EGHR bypass valve
42 is switched, flipped, or otherwise actuated to a bypass
position--shown in FIG. 1 as a dashed line and labeled as element
43--exhaust gases leaving the engine 12 are not allowed to pass through
the EGHR heat exchanger 18.

[0027] The EGHR bypass valve 42 may be controlled by a solenoid, a
mechanical thermostat, a wax motor, vacuum actuator, or other suitable
controls, and may be switched between the non-bypass position and the
bypass position at varying temperatures and conditions. The EGHR bypass
valve 42 may be controlled based upon the monitored engine temperature or
based upon the temperature of the coolant flowing through the EGHR heat
exchanger 18. For example, and without limitation, the EGHR bypass valve
42 may be a wax motor driven by coolant temperatures of seventy-two
degrees Celsius or greater in the engine water circuit 22. The set-point
temperature for the EGHR bypass valve 42, and other settings within the
EGHR system 10, is exemplary and illustrative only. The specific values
for set points will be determined based upon the specific configuration
of the EGHR system 10 and the vehicle into which it is incorporated.

[0028] A transmission thermostat 44 controls flow between the transmission
oil circuit 28 and the transmission radiator 34. The transmission
thermostat 44 is shown in its direct return position, which directs flow
of exhaust returning from the central heat exchanger 36 back to the
transmission 14 without passing through the transmission radiator 34.
When the transmission thermostat 44 is switched, flipped, or otherwise
actuated to a radiator position--shown in FIG. 1 as a dashed line and
labeled as element 45--oil returning from the central heat exchanger 36
is directed through the transmission radiator 34 before returning to the
transmission 14.

[0029] When the transmission thermostat 44 is in the radiator position (as
shown as 45 in FIG. 1) heat may be transferred or communicated from
either the transmission 14 or the central heat exchanger 36 to the
ambient air via the transmission radiator 34. For example, and without
limitation, the transmission thermostat 44 may be a mechanical or an
electromechanical thermostat opened by oil temperatures greater than
eighty-two degrees Celsius or greater than ninety-two degrees Celsius in
the transmission oil circuit 28, depending upon the size of the
transmission radiator 34.

[0030] Flow arrows are shown in FIG. 1 in order to illustrate the path and
direction of flow through some areas and components of the EGHR system 10
during specific operating modes. The EGHR bypass valve 42 is shown in the
non-bypass modes so that exhaust gases are flowing through the EGHR heat
exchanger 18. The transmission thermostat 44 is shown in the direct
return position so that oil is not passing through the transmission
radiator 34. The two-way valve 26 is shown in the transmission position
so that the transmission water circuit 24 is in fluid communication with
the engine water circuit 22. When the two-way valve 26 is in the
transmission position the central heat exchanger 36 allows heat-exchange
communication between the engine water circuit 22 (via the transmission
water circuit 24) and the transmission oil circuit 28.

[0031] An ambient air sensor 46 monitors the temperature of the ambient
air around (and flowing through) the vehicle and is in communication with
the control system 20. Either the control system 20 or the ambient air
sensor 46 compares the monitored ambient air temperature to one of a
calibrated cold ambient temperature, a calibrated mild ambient
temperature, and a calibrated hot ambient temperature. Each of the
calibrated temperatures referred to herein may be determined through
testing or modeling of the EGHR system 10 and the vehicle. Furthermore,
the calibrated temperatures may be altered throughout the lifetime of the
vehicle based upon the lifecycle of the vehicle or components thereof or
based upon learned operating characteristics of the vehicle of having the
EGHR system 10. The values given for the calibrated temperatures are
illustrative and exemplary only, and the values are not intended to limit
the scope of the invention unless included in the claims defining the
invention.

[0032] Referring now to FIGS. 2-5, and with continued reference to FIG. 1,
there are shown schematic flow chart diagrams of an algorithm or method
200 for controlling exhaust gas heat recovery, such as the EGHR system 10
shown in FIG. 1. The exact order of the steps of the algorithm or method
200 shown in FIGS. 2-5 is not required. Steps may be reordered, steps may
be omitted, and additional steps may be included. Furthermore, the method
200 may be a portion or sub-routine of another algorithm or method.

[0033] For illustrative purposes, the method 200 may be described with
reference to the elements and components shown and described in relation
to FIG. 1 and may be executed by the control system 20. However, other
components may be used to practice the method 200 and the invention
defined in the appended claims. Any of the steps may be executed by
multiple components within the control system 20.

[0036] The method 200 may begin at a start or initialization step, during
which time the method 200 is monitoring operating conditions of the
vehicle and of the EGHR system 10. Initiation may occur in response to
the vehicle operator inserting the ignition key or in response to
specific conditions being met, such as in response to a negative torque
request (braking or deceleration request) from the driver or cruise
control module combined with a predicted or commanded downshift.
Alternatively, the method 200 may be running constantly or looping
constantly whenever the vehicle is in use.

[0038] The method 200 includes monitoring or determining temperatures of
different components or conditions. An ambient air temperature is
monitored, such as with the ambient air sensor 46. An engine water
temperature is also monitored. The engine water temperature may be
determined from within the engine 12, at the entrance to the engine water
circuit 22, or from another location of the engine water circuit 22. A
transmission oil temperature is also monitored. The transmission oil
temperature may be determined from within the transmission 14, at the
entrance to the transmission oil circuit 28, or from another location.

[0039] Step 214: Compare Ambient Air to Calibrated Temperatures.

[0040] The method 200 compares the monitored ambient air temperature to
the calibrated cold ambient temperature, the calibrated mild ambient
temperature, and the calibrated hot ambient temperature to determine the
ambient air temperature range. For example, and without limitation, the
calibrated cold ambient temperature may be any monitored ambient
temperature below eight degrees Celsius; the calibrated mild ambient
temperature may be any monitored ambient temperature between eight and
seventeen degrees Celsius; and the calibrated hot ambient temperature may
be any monitored ambient temperature above seventeen degrees Celsius.

[0041] If the method 200 determines that the temperature is within the
mild range, the method 200 proceeds to the mild sub-routine 300. If the
method 200 determines that the temperature is within the cold range, the
method 200 proceeds to the cold sub-routine 400. If the method 200
determines that the temperature is within the hot range, the method 200
proceeds to the hold sub-routine 500.

[0042] Mild Sub-Routine 300.

[0043] Referring now to FIG. 3, and with continued reference to FIGS. 1-2,
there is shown a schematic flow chart diagram of the mild sub-routine
300. The mild sub-routine 300 is a portion of the method 200 shown in
FIG. 2 and is represented in FIG. 2 as a part of the block denoted by the
number 300. The steps shown in the flow chart diagram of FIG. 3 may be
only a portion of the mild sub-routine 300, such that the method 200 may
include further steps within the mild sub-routine 300. The mild
temperature range occurs when the ambient air temperature is monitored to
be between the cold temperature range and the hot temperature range.

[0044] Step 310: Engine Temperature Less than Calibrated First
Temperature?

[0045] The method 200 includes comparing the monitored engine water
temperature to a calibrated first engine temperature. For example, and
without limitation, the calibrated first engine temperature may be
approximately sixty degrees Celsius.

[0048] If the method 200 determines that the monitored engine water
temperature is below the calibrated first engine temperature, the method
200 proceeds to an engine-warming mode for the EGHR system 10. Depending
upon the configuration of the engine 12, operating below the calibrated
first engine temperature may affect fuel efficiency. Therefore, the
method 200 places the EGHR system 10 into the engine-warming mode to
increase the temperature of the engine 12 with any available heat from
the exhaust gases through the EGHR heat exchanger 18.

[0049] Step 314: Valve Set to Engine Position.

[0050] If the monitored engine water temperature is below the calibrated
first engine temperature, then execution of the engine-warming mode
includes controlling (setting) the two-way valve 26 to the engine
position. The control system 20 may actuate the two-way valve 26 based
upon the determination of the method 200. Furthermore, the EGHR bypass
valve 42 is calibrated to remain in the non-bypass position because the
temperature of the coolant passing through the engine water circuit 22 is
insufficient to actuate or trigger the bypass valve.

[0051] When in the engine-warming mode, hot exhaust gases travel through
the exhaust system 16 and are directed through the EGHR heat exchanger 18
by the EGHR bypass valve 42. Coolant leaves the engine 12 and passes
through the heater core 30. The two-way valve 26 prevents flow of the
coolant through the transmission water circuit 24, so the coolant is
circulated only through the engine water circuit 22. The exhaust gases
transfer heat to the coolant in the engine water circuit 22, which
returns to the engine 12 and warms the engine 12.

[0052] Although the transmission water circuit 24 has no flow, the
transmission oil circuit 28 may be circulating oil through the central
heat exchanger 36. The temperature of the transmission 14 is
substantially controlled by heat generated within the transmission 14 and
by heat dissipated through the transmission radiator 34 if the
transmission thermostat 44 moves to the radiator position.

[0053] The method 200 may stay in engine-warming mode with the two-way
valve 26 set to the engine position for a pre-determined or a calculated
time period. However, the method 200 may be looping or iterating
repeatedly and the engine-warming mode may continue until a subsequent
loop determines that conditions of the EGHR system 10 have changed, and
the method 200 results in another operating mode.

[0054] Step 316: Transmission Temperature Less than Calibrated First
Temperature?

[0055] If the method 200 determines that the monitored transmission oil
temperature is at or above (i.e. not below) the calibrated first engine
temperature, then the method 200 does not need to enter the
engine-warming mode. The method 200 then includes comparing the monitored
transmission oil temperature to a calibrated first transmission
temperature. For example, and without limitation, the calibrated first
transmission temperature may be approximately eighty degrees Celsius.

[0056] Depending upon the configuration of the transmission 14, operating
below the calibrated first transmission temperature may affect fuel
efficiency. However, the transmission 14 may be negatively effected if
the monitored transmission oil temperature too hot.

[0057] Step 318: Transmission-Warming Mode.

[0058] If the monitored transmission oil temperature is below the
calibrated first transmission temperature and the monitored engine water
temperature is below the calibrated first engine temperature, then the
method 200 will control the EGHR system 10 to a transmission-warming
mode. In the transmission-warming mode, heat from the engine 12, the EGHR
heat exchanger 18, or both, is transferred through the central heat
exchanger 36 to the transmission oil circuit 28 and the transmission 14.

[0059] Step 320: Valve Set to Transmission Position.

[0060] When in the transmission-warming mode, the method 200 includes
setting the two-way valve 26 to the transmission position. When the
two-way valve 26 is in the transmission position, coolant passes through
the heater core 30 and is then directed through the transmission water
circuit 24 and the central heat exchanger 36 before proceeding to the
EGHR heat exchanger 18 and back to the engine 12. Any time that the EGHR
system 10 is in the transmission-warming mode, the two-way valve 26 will
be set to the transmission position.

[0061] During the transmission-warming mode, heat from the engine 12 will
be transferred through the central heat exchanger 36 to the transmission
14. Furthermore, heat from the exhaust gases will transfer from the EGHR
heat exchanger 18 to the engine water circuit 22 to either raise the
temperature of engine 12 or to replenish the heat transferred to the
transmission 14. If the temperature of the engine rises substantially
during the transmission-warming mode, the EGHR bypass valve 42 will close
(driven by, for example, the wax motor) to the bypass position (shown as
43 in FIG. 1) and prevent heat from exhaust gases from passing to the
engine water circuit 22. The transmission-warming mode is shown in FIG. 1
where the two-way valve 26 is allowing heat-exchange communication
between the EGHR heat exchanger 18, the engine 12, and the transmission
14.

[0062] Like the engine-warming mode, the method 200 may stay in
transmission-warming mode with the two-way valve 26 set to the
transmission position for a pre-determined or a calculated time period.
However, the method 200 may be looping or iterating repeatedly and the
transmission-warming mode may continue until a subsequent loop determines
that conditions of the EGHR system 10 have changed, and the method 200
results in another operating mode. Whenever the EGHR system 10 is in the
transmission-warming mode, the two-way valve 26 will be set to the
transmission position.

[0063] Step 322: Transmission Cooling Mode.

[0064] If the monitored transmission oil temperature is above the
calibrated first transmission temperature and the monitored engine water
temperature is below the calibrated first engine temperature, then the
method 200 will control the EGHR system 10 to a transmission cooling
mode. In the transmission cooling mode, heat from the transmission 14 is
either retained within the transmission oil circuit 28 or dissipated
through the transmission radiator 34.

[0065] Step 324: Valve Set to Engine Position.

[0066] When in the transmission cooling mode, the method 200 includes
setting the two-way valve 26 to the engine position. When the two-way
valve 26 is in the engine position, no coolant flow occurs in the
transmission water circuit 24. Therefore, heat is not exchanged through
the central heat exchanger 36 to the transmission 14.

[0067] During the transmission cooling mode, coolant continues to flow
through the engine water circuit 22 and the temperature of the engine 12
will be controlled solely by the EGHR bypass valve 42. Oil continues to
circulate through the transmission oil circuit 28. However, because no
coolant is flowing through the central heat exchanger 36, no heat will be
transferred to the transmission 14. If the temperature of the
transmission 14 rises above the level necessary to actuate or trigger the
transmission thermostat 44, fluid will flow through the transmission
radiator 34 and dissipate heat from the transmission oil circuit 28,
thereby cooling the transmission 14.

[0068] Cold Sub-Routine 400.

[0069] Referring now to FIG. 4, and with continued reference to FIGS. 1-3,
there is shown a schematic flow chart diagram of the cold sub-routine
400. The cold sub-routine 400 is a portion of the method 200 shown in
FIG. 2 and is represented in FIG. 2 as a part of the block denoted by the
number 400. The steps shown in the flow chart diagram of FIG. 4 may be
only a portion of the cold sub-routine 400, such that the method 200 may
include further steps within the cold sub-routine 400. The cold
temperature range occurs below the mild temperature range. The cold
sub-routine 400 may be called-up whenever the method 200 determines that
the ambient temperature is below the calibrated cold ambient temperature.

[0070] Step 410: Engine Temperature Less than Calibrated Second
Temperature?

[0071] If the monitored ambient air temperature is below the calibrated
cold ambient temperature, the method 200 includes comparing the monitored
engine water temperature to a calibrated second engine temperature. The
calibrated second engine temperature may be the same as or different from
the calibrated first engine temperature. For example, and without
limitation, the calibrated second engine temperature may be approximately
seventy-five degrees Celsius, while calibrated first engine temperature
is sixty degrees Celsius. The calibrated second engine temperature may be
greater than the calibrated first engine temperature because the
relatively colder ambient air temperature provides less heat to the
engine 12.

[0072] Step 412: Engine-Warming Mode.

[0073] If the method 200 determines that the monitored engine water
temperature is below the calibrated second engine temperature, the method
200 proceeds to the engine-warming mode for the EGHR system 10. The
method 200 places the EGHR system 10 into the engine-warming mode to
increase the temperature of the engine 12--if any heat is available from
the exhaust gases--through the EGHR heat exchanger 18.

[0074] Step 414: Valve Set to Engine Position.

[0075] Executing the engine-warming mode includes controlling or setting
the two-way valve 26 to the engine position. The control system 20 may
actuate the two-way valve 26 based upon the determination of the method
200. Furthermore, the EGHR bypass valve 42 is calibrated to remain in the
non-bypass position because the temperature of the coolant passing
through the engine water circuit 22 is insufficient to actuate or trigger
the bypass valve.

[0076] As during the engine-warming mode of the mild ambient sub-routine
300 shown in FIG. 3, when the EGHR system 10 is in the engine-warming
mode, hot exhaust gases travel through the exhaust system 16 and are
directed through the EGHR heat exchanger 18 by the EGHR bypass valve 42.
Coolant leaves the engine 12, passes through the heater core 30, and the
two-way valve 26 prevents flow of the coolant through the transmission
water circuit 24. The coolant is circulated only through the engine water
circuit 22. The exhaust gases transfer heat to the coolant in the engine
water circuit 22, which returns to warm the engine 12.

[0077] Step 416: Engine Producing Positive Torque?

[0078] If the method 200 determines that the monitored engine water
temperature is not below the calibrated second engine temperature, the
method 200 proceeds to monitoring for an auto-stop mode. Auto-stop mode
occurs when vehicles shut down, power off, or cut fuel to the engine 12.
Alternatively stated, auto-stop mode occurs when the engine 12 is not
producing positive torque.

[0079] Step 418: Transmission-Warming Mode.

[0080] If the engine 12 is not in auto-stop mode, such that the engine 12
is producing positive torque, then the method 200 will control the EGHR
system 10 to the transmission-warming mode. In the transmission-warming
mode, during cold ambient temperatures, heat from the engine 12, residual
heat from the EGHR heat exchanger 18, or heat from both, is transferred
through the central heat exchanger 36 to the transmission oil circuit 28
and the transmission 14.

[0081] Step 420: Valve Set to Transmission Position.

[0082] When in the transmission-warming mode, the method 200 sets the
two-way valve 26 to the transmission position. When the two-way valve 26
is in the transmission position, coolant passes through the heater core
30 and is then directed through the transmission water circuit 24 and the
central heat exchanger 36 before proceeding to the EGHR heat exchanger 18
and back to the engine 12. Any time that the EGHR system 10 is in the
transmission-warming mode, the two-way valve 26 will be set to the
transmission position.

[0083] During the transmission-warming mode, heat from the engine 12 will
be transferred through the central heat exchanger 36 to the transmission
14. Furthermore, heat from the exhaust gases left in the EGHR heat
exchanger 18 will transfer from the EGHR heat exchanger 18 to the engine
water circuit 22 and eventually to the transmission 14.

[0084] Step 422: Auto-Stop Mode.

[0085] If the engine 12 is in the auto-stop mode, the engine 12 is not
producing torque and is likely not producing heat. Furthermore, during
the auto-stop mode, the auxiliary pump 38 will be turned on to provide
pressure to the engine water circuit 22 and, if connected by the two-way
valve 26, to the transmission water circuit 24.

[0086] Step 424: Transmission Temperature Less than Calibrated Second
Temperature?

[0087] After determining that the engine 12 is in auto-stop mode, the
method 200 then includes comparing the monitored transmission oil
temperature to a calibrated second transmission temperature. For example,
and without limitation, the calibrated second transmission temperature
may be approximately seventy degrees Celsius, which is lower than the
first calibrated transmission temperature used in the mild ambient
temperature sub-routine 300.

[0088] Step 426: Transmission-Warming Mode.

[0089] If the engine 12 is in auto-stop mode and the monitored
transmission oil temperature is below the calibrated second transmission
temperature, then the method 200 will again control the EGHR system 10 to
the transmission-warming mode. In the transmission-warming mode, during
cold ambient temperatures, heat from the engine 12, residual heat from
the EGHR heat exchanger 18, or heat from both, is transferred through the
central heat exchanger 36 to the transmission oil circuit 28 and the
transmission 14.

[0090] Step 428: Valve Set to Transmission Position.

[0091] When in the transmission-warming mode, the method 200 sets the
two-way valve 26 to the transmission position. When the two-way valve 26
is in the transmission position, coolant passes through the heater core
30 and is then directed through the transmission water circuit 24 and the
central heat exchanger 36 before proceeding to the EGHR heat exchanger 18
and back to the engine 12.

[0092] During the transmission-warming mode, heat from the engine 12 will
be transferred through the central heat exchanger 36 to the transmission
14. Furthermore, heat from the exhaust gases left in the EGHR heat
exchanger 18 will transfer from the EGHR heat exchanger 18 to the engine
water circuit 22 and eventually to the transmission 14.

[0093] Step 430: Engine-Warming Mode.

[0094] If the method 200 determines that the engine 12 is in the auto-stop
mode (not producing torque) and if the monitored transmission oil
temperature is not below the calibrated second transmission temperature,
the method 200 proceeds to the engine-warming mode for the EGHR system
10. The method 200 places the EGHR system 10 into the engine-warming mode
to increase the temperature of the engine 12--if any heat is available
from the exhaust gases--through the EGHR heat exchanger 18. During
auto-stop mode, additional heat in the transmission 14 may be used as
additional thermal mass to delay the next engine-on event if the
transmission 14 is above the calibrated second transmission temperature.

[0095] Step 432: Valve Set to Engine Position.

[0096] Executing the engine-warming mode includes controlling or setting
the two-way valve 26 to the engine position. When the EGHR system 10 is
in the engine-warming mode, residual heat from hot exhaust gases is
directed through the EGHR heat exchanger 18 by the EGHR bypass valve 42.
Coolant leaves the engine 12, passes through the heater core 30, and the
two-way valve 26 prevents flow of the coolant through the transmission
water circuit 24. The exhaust gases transfer heat to the coolant in the
engine water circuit 22, which returns to warm the engine 12.

[0097] Hot Sub-Routine 500.

[0098] Referring now to FIG. 5, and with continued reference to FIGS. 1-4,
there is shown a schematic flow chart diagram of the hot sub-routine 500.
The hot sub-routine 500 is a portion of the method 200 shown in FIG. 2
and is represented in FIG. 2 as a part of the block denoted by the number
500. The steps shown in the flow chart diagram of FIG. 5 may be only a
portion of the hot sub-routine 500, such that the method 200 may include
further steps within the hot sub-routine 500. The hot temperature range
occurs above the mild temperature range.

[0099] The hot sub-routine 500 may be called-up whenever the method 200
determines that the ambient temperature is above the calibrated hot
ambient temperature. When the ambient air temperature is in the hot
range, the potential for heat degradation or damage to the engine 12 or
the transmission 14 is increased.

[0100] Step 510: Transmission Temperature Less than Calibrated First
Temperature?

[0101] The method 200 again includes comparing the monitored transmission
oil temperature to the calibrated first transmission temperature. If the
monitored transmission oil temperature is below the calibrated first
transmission temperature, then the transmission 14 is cold--even though
the ambient temperature is hot--and efficiency may be reduced.

[0102] Step 512: Transmission-Warming Mode.

[0103] If the monitored transmission oil temperature is below the
calibrated first transmission temperature and the monitored ambient air
temperature is above the calibrated hot ambient temperature, then the
method 200 will control the EGHR system 10 to a transmission-warming
mode. As in other ambient air temperatures, such as those shown in FIGS.
3 and 4, when the EGHR system 10 is in the transmission-warming mode,
heat from the engine 12 or from the EGHR heat exchanger 18, or both, is
transferred through the central heat exchanger 36 to the transmission oil
circuit 28 and the transmission 14.

[0104] Step 514: Valve Set to Transmission Position.

[0105] When in the transmission-warming mode, the method 200 includes
setting the two-way valve 26 to the transmission position. When the
two-way valve 26 is in the transmission position, coolant passes through
the heater core 30 and is then directed through the transmission water
circuit 24 and the central heat exchanger 36 before proceeding to the
EGHR heat exchanger 18 and back to the engine 12. Any time that the EGHR
system 10 is in the transmission-warming mode, the two-way valve 26 will
be set to the transmission position.

[0106] During the transmission-warming mode, heat from the engine 12 will
be transferred through the central heat exchanger 36 to the transmission
14. Furthermore, heat from the exhaust gases will transfer from the EGHR
heat exchanger 18 to the engine water circuit 22 to either raise the
temperature of engine 12 or to replenish the heat transferred to the
transmission 14. If the temperature of the engine rises substantially
during the transmission-warming mode, the EGHR bypass valve 42 will close
(driven by, for example, the wax motor) to the bypass position (shown as
43 in FIG. 1) and prevent heat from exhaust gases from passing to the
engine water circuit 22.

[0107] Step 516: Transmission Temperature not Cold.

[0108] If the monitored transmission oil temperature is not below the
calibrated first transmission temperature, then the method 200 does not
need to warm the transmission 14. The method 200 may then determine
whether either the engine 12 or the transmission 14 is experiencing
extremely high temperatures.

[0110] The method 200 includes comparing the monitored engine water
temperature to a calibrated extreme engine temperature or a calibrated
third engine temperature. The calibrated extreme engine temperature may
be based upon temperatures above which the engine 12 is likely to
degrade, if maintained for an extended period of time. For example, and
without limitation, the calibrated extreme engine temperature may be
approximately one hundred twenty degrees Celsius.

[0111] Step 520: Engine Temperature not Extreme.

[0112] If the method 200 determines that the monitored engine water
temperature is less than the calibrated extreme engine temperature, then
the engine 12 is not experiencing extreme temperatures. However, although
warming of the engine 12 may not be needed, the method 200 then sets the
two-way valve 26 to the engine position.

[0113] Step 522: Valve Set to Engine Position.

[0114] When the two-way valve 26 is set to the engine position, the
temperature of the engine 12 may warm, cool, or stay relatively constant.
If the temperature of the coolant in the engine water circuit 22 is below
the temperature necessary to actuate the EGHR bypass valve 42, heat will
be transferred from the exhaust gases to the engine 12. However, if the
temperature is above the level necessary to close the EGHR bypass valve
42--by actuating, for example, the wax motor--to the bypass position
(shown as 43 in FIG. 1), exhaust gases will be prevented from passing to
the engine water circuit 22. Note also that high temperatures within the
engine 12 may trigger the engine thermostat to begin flow through the
engine radiator 32 to cool the engine 12.

[0116] If the monitored engine water temperature is greater than the
calibrated extreme engine temperature, then the engine 12 is experiencing
extreme temperatures. The method 200 then proceeds to determine whether
the excess heat in the engine 12 may be dissipated through the
transmission 14 and the transmission radiator 34. Therefore, the method
200 includes comparing the monitored transmission oil temperature to a
calibrated extreme transmission temperature.

[0117] The calibrated extreme transmission temperature may be based upon
temperatures above which the transmission 14 is likely to degrade, if
maintained for an extended period of time. For example, and without
limitation, the calibrated extreme transmission temperature may be
approximately one hundred ten degrees Celsius. Note that when the
temperature of the engine 12 is above the calibrated extreme engine
temperature, the engine thermostat is likely allowing flow through the
engine radiator 32 and the EGHR bypass valve 42 is in the bypass position
(shown as dashed line 43 in FIG. 1).

[0118] Step 526: Engine Cooling Through the Transmission.

[0119] If the monitored transmission oil temperature is below the
calibrated extreme transmission temperature while the monitored engine
water temperature is greater than the calibrated extreme engine
temperature, then there is excess cooling capacity through the
transmission 14. Excess heat from the engine 12 may be transferred from
the engine 12 to the transmission oil circuit 28 and the transmission
radiator 34.

[0120] Step 528: Valve Set to Transmission Position.

[0121] The method 200 includes setting the two-way valve 26 to the
transmission position, such that the transmission radiator 34 is in
heat-exchange communication with the engine 12. Heat is transferred from
the engine 12 to the engine water circuit 22 and through the central heat
exchanger 36 to the transmission oil circuit 28.

[0122] If the temperature of the transmission oil circuit 28 rises above
the level necessary to actuate the transmission thermostat 44 to the
radiator position (shown as dashed line 45 in FIG. 1). Once the
transmission thermostat 44 allows flow through the transmission radiator
34, the excess heat transferred from the engine 12 is dissipated through
the transmission radiator 34. By setting the two-way valve 26 to the
transmission position, this configuration of the EGHR system 10 allows
excess heat from the engine 12 to be dissipated through the transmission
14 and the transmission radiator 34.

[0123] Therefore, in certain conditions, the EGHR systems 10 may be placed
into engine-warming, engine-cooling, transmission-warming, or
transmission-cooling modes. The vehicle cabin may also be warmed through
the heater core 30. Operation of the EGHR system 10 in the various modes
is controlled by selection of the position of the two-way valve 26 based
upon monitored or determined temperatures of the ambient air, the engine
12, or the transmission 14.

[0124] Step 530: No Excess Cooling Capacity.

[0125] If the monitored engine water temperature is greater than the
calibrated extreme engine temperature and the monitored transmission oil
temperature is also greater than the calibrated extreme transmission
temperature, there is no excess cooling capacity available through the
transmission 14 or transmission radiator 34.

[0126] Step 532: Valve Set to Engine Position.

[0127] The method then sets the two-way valve 26 to the engine position,
such that the transmission radiator 34 is not in heat-exchange
communication with the engine 12. Therefore, the EGHR system 10 is
configured to only transfer heat to the transmission 14 when it is below
the calibrated extreme transmission temperature. When both the engine 12
and the transmission 14 are above their respective extreme temperatures,
the engine radiator 32 and the transmission radiator 34 are used to
dissipate heat.

[0128] The detailed description and the drawings or figures are supportive
and descriptive of the invention, but the scope of the invention is
defined solely by the claims. While some of the best modes and other
embodiments for carrying out the claimed invention have been described in
detail, various alternative designs and embodiments exist for practicing
the invention defined in the appended claims.

Patent applications by Brian L. Spohn, Holly, MI US

Patent applications by GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Patent applications in class Process of power production or system operation

Patent applications in all subclasses Process of power production or system operation